Why Can We Not Measure the Mass of Elliptical Galaxies

question 105

Multiple Choice

Why can we not measure the mass of elliptical galaxies using the 21- cm line of hydrogen gas?

• A)Supermassive black holes in the center of elliptical galaxies disturb measurements of the 21- cm line.
• B)The disorderly motion of the material in elliptical galaxies prevents us from measuring different velocities at different sides of the galaxy.
• C)All elliptical galaxies are too far away for us to detect the 21- cm line.
• D)Elliptical galaxies have little gas, so do not have strong 21- cm line emission.

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